How to measure how many board feet in different size trees.

[josh79]

I have a sawmill that said they would pay 16-18 cent per board foot for any straight 10 foot logs that I bring. What math equation do I use to find how many board feet I could possibly sell when I go to bid for various clients?

 

[Metals406]

You could calculate the logs using the formula for the "Frustum of a cone". . . V= 3.14 (r1 +R2) h/3

Measure the radius on the small end, and measure the radius on the big end, and add the two numbers. . . Now times that total by 3.14, times that by the length of the log, divide that by three.

That would give you cubic inches, there are 144 cubic inches in one board foot--so divide your log total by 144.

I highly doubt they'll pay you for the whole thing, so you'd want to figure out usable board feet, as follows:

If you were looking to cut equal slabs from the log, not all of its
volume would be recoverable. Picture a square inscribed in (set
inside) a circle. If everything outside the square is cut away, then
the diameter of the circle becomes the diagonal of the square.

So in that case the usable volume of the log would be the area of that
square times the length of the log.
The area of a square in terms of its diagonal is
(d * d)/2
so in this case the usable board feet are
(d * d)/2 * L * 1/144
which is about 64% of the full volume of the log

 

[pdqdl]

doyle method board feet

There are several different schemes for calculating the board feet in a log. It is pointless to learn all the different ways to come up with your own board feet measure: the only thing that counts is how your buyer measures what you are selling.

Ask the buyer what method of lumber calculation he uses.

One method you might check is the Doyle method:

http://www.google.com/url?sa=t&sour...jYpaEL&usg=AFQjCNEMf92m34ljtw6P3qi4I-PFQvUf1A

Here is an excellent article on the topic: http://www.google.com/url?sa=t&sour...jYpaEL&usg=AFQjCNEQzTDwPDg9LaSy7ImzZc45_N-7Dg

As you can see, there are no easy answers for how many board feet you will get paid for.

 

[VA-Sawyer]

Some of these folks have no idea how to scale a log. PDQDL is the only one on the right track.
I have owned a Woodmizer since 2003 and have cut over 100,000 bf of lumber. Forget the formula's, use a Scale Table instead. There are over 100 different log scales used in commerical trade, but only 3 are considered common, Doyle, Scribner and 1/4 International. Find out which one your mill uses, and then go online and print out the Table for that scale. Print out the rules for the scale as well. Most scales use the diameter inside the bark on the small end and the length in whole feet, ( no rounding up ) to get bf for a given log. There are deductions for defects such as rot and sweep (bend) among many others.

Scale up a load of logs to get a total and then compare your figure to the one the mill adds up. If your figure is within 5% of the mill figure then all is well. If your figure is a lot higher than the mill figure then ask the buyer where you went wrong in your scaling. ( At first, I suggest that you assume he is not cheating you, maybe you forgot to deduct for a defect.) Maybe use a marker to write your bf calculation on the end of each log. The buyer should be able to clearly explain why a log scales lower than you think it should. Make sure he understands that you are trying to learn how to properly scale a load. If he can't explain the difference or isn't willing to help you tune up your scaling skills a little, then maybe try looking for a different mill.
Rick

 

[Metals406]

Some of these folks have no idea how to scale a log. PDQDL is the only one on the right track.
I have owned a Woodmizer since 2003 and have cut over 100,000 bf of lumber. Forget the formula's, use a Scale Table instead. There are over 100 different log scales used in commerical trade, but only 3 are considered common, Doyle, Scribner and 1/4 International. Find out which one your mill uses, and then go online and print out the Table for that scale. Print out the rules for the scale as well. Most scales use the diameter inside the bark on the small end and the length in whole feet, ( no rounding up ) to get bf for a given log. There are deductions for defects such as rot and sweep (bend) among many others.

Scale up a load of logs to get a total and then compare your figure to the one the mill adds up. If your figure is within 5% of the mill figure then all is well. If your figure is a lot higher than the mill figure then ask the buyer where you went wrong in your scaling. ( At first, I suggest that you assume he is not cheating you, maybe you forgot to deduct for a defect.) Maybe use a marker to write your bf calculation on the end of each log. The buyer should be able to clearly explain why a log scales lower than you think it should. Make sure he understands that you are trying to learn how to properly scale a load. If he can't explain the difference or isn't willing to help you tune up your scaling skills a little, then maybe try looking for a different mill.
Rick

The dude asked for a way to mathematically figure board feet of a ten foot log. He didn't ask for what log-scale to use.

I provided him with two ways of accurately figuring cubic feet and board feet. You are correct that a buyer will use a scale (most likely). . . But as Matthew Fonseca wrote in his book "The Measurement of Roundwood, methodologies and conversion ratios". . . When speaking of log scaling:

Log scales use the same equations I listed. . . No need to sit on a high horse, and belittle other posters.

 

[valekbrothers]

Here is some more good info on figuring bd. ft. on a log.

http://www.woodweb.com/knowledge_base/Measuring_Logs_and_Lumber.html

 

[VA-Sawyer]

Sorry if I came off sounding like I was on a high horse. I do however get frustrated with folks thinking a bf in the log is the same as a bf coming off the planer. At the mill we don't talk about a 1" board, we call it 4/4 ( four quarters) thick. Now you might think it is the same thing but it really isn't because a 4/4 board should actually measure between 1 1/16 and 1 1/8 inches thick coming off the mill. There are simular allowances for 5/4, 6/4, 8/4 etc. This allows for shrinkage during drying and will result in a board thick enough to plane out at 3/4" thick ( nominal 1" board ) without being overthick going into the planer. A boardfoot doesn't have to have any specific width or thickness. It can be 4/4 square and 12' long or 6"w by 4"t by 6"long. It just means 144 cubic inches.
As the OP asked how much he could sell to the mill, I would like to point out that you can't sell the fat end of the log. Geometric calculations will probably result in inflated expections of log values. Not much good when trying to decide if it is worth hauling to the mill vs selling as firewood. Do mills get more BF out of a log than the Scale calls for? Usually they do, and the term is overrun. Do they pay the log seller for it? Almost never! Buying and selling logs is very different from buying or selling lumber. Way more unknowns in logs. The mills want to shove as much of the risk as possible onto the log sellers. If the log has more taper than normal, it takes more time to saw for grade. By paying for the small end ( inside bark) they will get a little more money from the overrun to help cover the extra time required.
From time to time a mill will do runs where they use careful volume calculations from each log and compare it to the expected Scale yield and the actual yield. They use this info to evaluate the efficiency of the milling operation. They also will use it to develope their own log scales in some cases. All this relates to the sawing side of the mill and normally only affects the price paid per bf, not the bf figured in a load of logs. ( Custom log scales being the exception here )
Rick

 

[Metals406]

Sorry if I came off sounding like I was on a high horse. I do however get frustrated with folks thinking a bf in the log is the same as a bf coming off the planer. At the mill we don't talk about a 1" board, we call it 4/4 ( four quarters) thick. Now you might think it is the same thing but it really isn't because a 4/4 board should actually measure between 1 1/16 and 1 1/8 inches thick coming off the mill. This allows for shrinkage during drying and will result in a board thick enough to plane out at 3/4" thick ( nominal 1" board ) without being overthick going into the planer. A boardfoot doesn't have to have any specific width or thickness. It can be 4/4 square and 12' long or 6"w by 4"t by 6"long. It just means 144 cubic inches.
As the OP asked how much he could sell to the mill, I would like to point out that you can't sell the fat end of the log. Do mills get more BF out of a log than the Scale calls for? Usually they do, and the term is overrun. Do they pay the log seller for it? Almost never! Buying and selling logs is very different from buying or selling lumber. Way more unknowns in logs. The mills want to shove as much of the risk as possible onto the log sellers. If the log has more taper than normal, it takes more time to saw for grade. By paying for the small end ( inside bark) they will get a little more money from the overrun to help cover the extra time required.
From time to time a mill will do runs where they use careful volume calculations from each log and compare it to the expected Scale yield and the actual yield. They use this info to evaluate the efficiency of the milling operation. They also will use it to develope their own log scales in some cases. All this relates to the sawing side of the mill and normally only affects the price paid per bf, not the bf figured in a load of logs. ( Custom log scales being the exception here )
Rick

 

[VA-Sawyer]

Adding a monkey wrench to the works......

While the Scale tables, and following the scale rules will allow a logger to estimate the bf and hence the value of a log, they should not be used to figure the weight. Scale tables tell you the approximate amount of lumber in a log, not the amount of wood. Using bf calculations to figure log weight will give numbers lighter than actual weights. To allow maximum trailer loads while avoiding overweight conditions and safety problems, the weights should be calculated using either geometric formulas or green log weight tables using a diameter that is an average of the large and small ends of the log. This is also true when figuring branch weights and rope loads in tree work except you should add in for the weight of the leaves and the minor branching as well when removing complete limbs.
Rick

 

[VA-Sawyer]

First off, let me give you my smarta$$ answer.... I hope they are veneer grade and he is bringing them to my mill.

As I said before, there is a lot of risk in buying logs. Back when I was still living in Williamsburg VA, I had a customer bring a Black Walnut log over from West Point for me to saw up for him. I jumped up on the trailer and looked the log over before unloading it to the mill. After a quick inspection ( mostly looking for metal ), I thought he had a nice log and was looking forward to seeing what kind of color and grain the boards would have. Imagine our surprise when cutting off one of the slabs we discovered the log was hollow and filled with rot mud. The rot started about 6" from one end and went to about a foot from the other end. A much closer inspection of the slabs found 2 small holes from dead branches about the size of my little finger. We should have gotten about 120 bf of nice lumber from that log, instead we got about 20 bf of low grade wood.
When I first saw the rot, I offered to kick the log off the mill and not charge him anything for my time. He wanted to keep sawing just to try to get something out of his time and travel. He even paid the full price for my saw time. As that was our first meeting, I never expected to see him again. Turned out to be a good customer and brought over a number of logs for me to saw. Ask me about sawing a Cedar log for him if you want a real sad story.

Back to the question about a load of Black Walnut.

The OP needs to do some research to learn the different values of different types of logs and how to grade them. He also needs to visit a few mills in the area to learn which mills are looking for what kinds of logs.
Larger mills today seem to focus on a smaller ( and more selective ) segment of the business. Some mills want only one or two kinds of wood. Some only want logs in a certain size range, such as 10 - 16 inches DIB. Because of this specialization, some mills may have no real desire to saw nice large Black Walnut logs. (However, they may buy them and resell to another mill that saws hardwood for grade. )
A small time logger or a tree service that has a wide range of log size and types, may get a better return by selling their logs to a forwarding yard or a small mill operation. Another option would be to have a portable mill come in and turn the logs into lumber for you. You could then sell the lumber green or build yourself a solar kiln and dry it for an even better return on your investment. ( I still drag my mill back to Williamsburg - 8 hrs each way- about twice a year for customers I still have there.)
Many of the state universities in tree country, work with their state extension office and publish timber prices for the area. Try to google "timber prices" or "log prices" for more info.
Rick

 

[BlackenedTimber]

For 16-18 cents per board foot, I wouldn't even waste my time. Firewood, bro.

What species and what specs are bringing 16-18 cents per board foot?